BK Boo-Boo!

15 replies to this topic
  • Psycho426

Posted November 12, 2001 - 09:54 AM


Did the BK mod this evening, adjusted the delay so it just missed the slide and set the duration to .3s, the bike started first kick no problem :D , waked the throttle right open (from idle just to see the response and how she revs) and she died on me straight away :)

I fiddled around with my fuel screw, made it richer and she still died :D made it leaner... still fell flat on her back :D

I'm going to tinker a bit to see if I can get it sorted, if not it's back to stock for me.

Does anyone have any suggestions ???

  • forloop

Posted November 12, 2001 - 11:03 AM


I had the same problem. I had to add more delay to get it right. Turn the delay screw in about a 1/2 turn.

  • yzernie

Posted November 12, 2001 - 12:25 PM


You may also have to increase the pilot jet by a size or two.

  • bbeakley

Posted November 12, 2001 - 01:00 PM


Don't remember which thread, but someone mentioned that the timing is different in neutral and even with the BK mod the bike is likely to die when you go to WOT quickly. Real way to judge is to get it out and ride it.

  • motojunkie

Posted November 12, 2001 - 01:02 PM


Try turning on the fuel petcock. LOL! :)

  • MX_Tuner

Posted November 12, 2001 - 03:26 PM


Yeah, that's an easy one. Don't yank the throttle wide open from an idle.

Seriously, go RIDE the bike and see how it runs. How can you possibly tell anything by revving it up standing still?

  • Psycho426

Posted November 12, 2001 - 08:31 PM


I'll give it a burn tonight, see how she runs. I'll let you guys know how it went.

  • MikeOK

Posted November 13, 2001 - 04:10 PM


psycho how did it turn out? I am planning on this one for a winter project for mine...

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  • Scott_in_KC

Posted November 13, 2001 - 05:39 PM


You might, MIGHT have to raise the needle (lower the clip) one spot. I found .5 sec worked best for mine. Regardless, you have to make up for the fuel that's no longer there in that rediculously long squirt that it had before the mod.

  • Psycho426

Posted November 13, 2001 - 08:43 PM


I went riding last night with the mod after turning the accelerator pump timing screw in half a turn as per Forloop's instructions...

That very noticeable ,long , bog that was there when you waked open the throttle has been reduced by at least 3/4, now when I waked open the throttle there is only a slight hesitation before she lets rip like bat out of hell. Guess that slight hesitation that’s left might just be jetting. My jetting was stock (162,42,clip4) before I did the mod, I'm at 5000-5500 ft and the avg. temp is 80. I'll move the needle clip one down (clip5) as per your instructions Scott.

Mike - Go for gold it makes a huge difference and I think after you get the jetting dialled in it will be a totally different bike

According to Motoman’s jetting chart I’m way to rich (what should I change in the chart to compensate for the BK mod ?).

Do you guys have any suggestions for my Main, Pilot and fuel screw?

[ November 16, 2001: Message edited by: Psycho426 ]

  • yzernie

Posted November 13, 2001 - 08:53 PM


I'm at 4000' and I had to go to a 45 pilot, dropped the needle one clip position and a 165 main. I use race gas so I jet a bit leaner than if I used pump gas. I have tried several different combos for the jetting and this seems to be the best so far (for me). The bike rips....no bog and pulls hard from bottom to top.

Hope this helps you a bit, Ernie

  • Psycho426

Posted November 13, 2001 - 09:01 PM


Thanx Ernie, I'll give those settings a shot, see how she runs.

Man, I can't wait to get the jetting right :)

  • urla

Posted November 14, 2001 - 02:45 AM


Psycho, if you turn the "the accelerator pump
timing screw in half a turn" , you also have to
turn the "BK mod screw" half a turn to keep your
.3 duration.
Having .6mm between "BK mod screw" and "plastic"
== ~.3 - .5sec duration.

  • Psycho426

Posted November 14, 2001 - 03:01 AM


Did that, undid the mod and resetup everything, setting the timing first then the duration.

[ November 14, 2001: Message edited by: Psycho426 ]

  • forloop

Posted November 14, 2001 - 04:22 AM


I run the BK mod with .5 seconds duration. My bike run great with out the BK mod. But, I figured there was some fine tunning to be gained.

My slide is about a 1/8 of the way up before the pump kicks in. The little bog of bottom is that first 1/8 travel of the slide. I am sure this can be jetted out. But, it does not affect me one bit at the track so I have not bothered.

I also believe that is you want to run a little longer duration say .7 seconds then you could start the pump sooner and reduce the bog more.

Good Luck,

  • Psycho426

Posted November 14, 2001 - 04:48 AM


I'll tinker around, see what works and what doesn't, might take a while to get everything perfect but I'll post my final settings jetting, duration etc. when it's 100% (if I ever get it 100% :) ).

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